Nonstandard Roughness of Terraced Surfaces

URL:http://link.aps.org/doi/10.1103/PhysRevLett.85.3894 DOI:10.1103/PhysRevLett.85.3894We present a class of surfaces which are simultaneously flat and rough over the same range of lengths. They are self-affine, have well-defined roughness exponents, and consist of terraces of all sizes. The coexistence of flat and rough makes them respond to different external interactions with variable roughness. We demonstrate this for optical scattering (including x rays), two wetting situations, diffusion currents, and catalysis. A terraced Cu surface is a “self-assembled” experimental example, and designs for nano- and micromachined examples are presented.We thank J.-K. Zuo, P. Miceli, F. Family, B. Sapoval, and M.-O. Coppens for valuable discussions, and the Petroleum Research Fund for support

Synergetic Utilization of Renewable and Fossil Fuels: Dual Fluidized Bed Steam Co-gasification of Coal and Wood

AbstractGasification of biomass and coal is an attractive technology for combined heat and power production, as well as for synthesis processes such as the production of liquid and gaseous biofuels. The allothermal steam blown gasification process yields a high calorific product gas, practically free of nitrogen. Originally designed for wood chips, the system can also handle a large number of alternative fuels. To demonstrate the influence on the system performance of fuels that have a different origin, wood pellets, as the designated feedstock, and hard coal as an example fossil fuel were fed into the DFB gasifier with a fuel blend ratio of 20% coal in terms of energy. A fuel power of 78kW and a steam to fuel ratio of 1.0kg/kgdb were achieved. The system was operated at gasification temperatures between 830 and 870°C. This paper points out the influence of the temperature on the system

Cost and Benefit of Apprenticeship Training: A Comparison of Germany and Switzerland

For the first time it has been made possible to merge a German and a Swiss firm-level data set that include detailed information about costs and benefits of apprenticeship training. Previous analyses based only on aggregate data showed that the net costs of training apprentices are substantial in Germany, whereas apprenticeship training is on average profitable during the training period for firms in Switzerland, even though the two training systems are rather similar. This paper analyzes the reasons for these differences with matching methods. We simulate the impact of changes in certain parameters such as wages, apprenticeship system-related factors and allocation of tasks to apprentices on the cost-benefit ratio using the counterfactual values of the other country. The results show that most of the difference in the net costs of training between the two countries can be explained by a higher share of productive tasks allocated to apprentices in Switzerland and the differences in relative wages.apprenticeship training, cost and benefit analysis

INVESTIGATION OF REFORMING ACTIVITY AND OXYGEN TRANSFER OF OLIVINE IN A DUAL CIRCULATING FLUIDISED BED SYSTEM WITH REGARD TO BIOMASS GASIFICATION

Natural olivine (Mg,Fe)2SiO4 is examined in a dual circulating fluidised bed (DCFB) reactor system of 120 kWth with regard to its reforming activity. Further, the oxygen transport capacity due to redox-cycling of the iron containing part of the olivine is considered. Based on a syngas composition derived from biomass gasification, the olivine is exposed to a surrogate gas mixture of H2, CO, CO2, CH4 and a tar compound (1-methylnaphthalene) at 850 °C. The results show the tar conversion at different tar loads. The investigations reveal that a low content of oxygen is transported by the olivine due to the redox-cycling in the reactor system

Experimental Study on Reforming Activity and Oxygen Transfer of Fe- Olivine in a Dual Circulating Fluidized Bed System

Fe-olivine was investigated in a dual circulating fluidised bed reactor system with focus on hydrocarbon reforming activity and effects of oxygen transfer. H2, CO2, CH4 and 1-methylnaphthalene were fed as a surrogate gas mixture to the reforming part. Oxygen transport was developed by solids circulation. Tar decomposition was marginally affected by partial oxidation. The overall degree of tar decomposition was found to be in the range of 70 to 80%

Charakterisierung spontaner Muriner Medulloblastome Im Heterozygoten Patched^+/--Knockout-Modell : Untersuchungen zu Histologie, Zellzyklus, Chemosensibilität und Promininexpression

Medulloblastome sind die häufigsten malignen Hirntumore bei Kindern. Trotz einer Kombination aus operativer, Bestrahlungs- und Chemotherapie kann nur bei 50-70 % der Patienten ein ereignisfreies Überleben über 5 Jahre erzielt werden. Die aktuelle Therapie verursacht bei einem großen Teil der Patienten schwere Langzeitschäden. Angesichts dieser Situation ist es dringend erforderlich, die angewandten Methoden weiter zu verbessern und neue Therapieoptionen zu erforschen. Dabei wird eine große Hoffnung mit der Entwicklung von Medikamenten verbunden, die spezifisch auf essentielle molekulare Prozesse der Tumore einwirken. Die Identifikation und Charakterisierung von Tumorstammzellen haben eine enorme Bedeutung für das Verstehen der Tumorgenese und Entwicklung von neuen therapeutischen Strategien. In dieser Arbeit werden Methoden evaluiert, die es ermöglichen, die Wirkung von Substanzen auf Medulloblastome in vivo mit dem Pached+/--Knockout-Mausmodell zu analysieren. Eine genaue Verlaufsdokumentation konnte durch die intravitale Magnet Resonanz Tomographie ermöglicht werden. Wir führten an Maus-Medulloblastomen histologische Färbungen zur Darstellung von Proliferation, Apoptosen, Differenzierung und dem Stammzellmarker Prominin durch. Ergänzend wurden in vitro Versuche an einer murinen Medulloblastomlinie durchgeführt. Es konnten darüber hinaus Erkenntnisse über das Signalweg-spezifisch wirkende Cyclopamin gewonnen werden. Wir konnten allerdings bei Applikation von Cyclopamin allein keine Verringerung des Wachstums oder eine verstärkte Differenzierung bei manifester Tumorerkrankung feststellen. Unsere Zellkulturversuche erbrachten bei der Kombination von Cyclopamin und Etoposid bei einigen Konzentrationen eine Wirkungsverstärkung. Wir konnten Prominin-positive Zellen an histologischen Schnitten von Patched+/--Tumoren und innerhalb der Zelllinie SJMM4 darstellen. Die Zellzyklusanalyse zeigte, dass Prominin-positive Zellen der Linie SJMM4 häufiger als negative im Zellzyklus anzutreffen sind. Signalweg-spezifische Wirkstoffe stellen eine wichtige Perspektive für zukünftige Therapieoptionen dar

Dynamics of Gas Exchange through the Fractal Architecture of the Human Lung, Modeled as an Exactly Solvable Hierarchical Tree [abstract]

Abstract of a presentation given at the 2008 Body Project conference at the University of Missouri-Columbia.The acinar airways lie at the periphery of the human lung and are responsible for the transfer of oxygen from air to the blood during respiration. This transfer occurs by the diffusion-reaction of oxygen over the irregular surface of the alveolar membranes lining the acinar airways. We present an exactly solvable diffusion-reaction model on a hierarchically branched tree, allowing a quantitative prediction of the oxygen current over the entire system of acinar airways responsible for the gas exchange. We discuss the effect of diffusional screening, which is strongly coupled to oxygen transport in the human lung. We show that the oxygen current is insensitive to a loss of permeability of the alveolar membranes over a wide range of permeabilities, similar to a "constantcurrent source" in an electric network. Such fault tolerance has been observed in other treatments of the gas exchange in the lung and is obtained here as a fully analytical result

Bimanual coordination associated with left- and right-hand dominance: testing the limb assignment and limb dominance hypothesis

In an experiment conducted by Kennedy et al. (Exp Brain Res 233:181–195, 2016), dominant right-handed individuals were required to produce a rhythm of isometric forces in a 2:1 or 1:2 bimanual coordination pattern. In the 2:1 pattern, the left limb performed the faster rhythm, while in the 1:2 pattern, the right limb produced the faster pattern. In the 1:2 pattern, interference occurred in the limb which had to produce the slower rhythm of forces. However, in the 2:1 condition, interference occurred in both limbs. The conclusion was that interference was not only influenced by movement frequency, but also influenced by limb dominance. The present experiment was designed to replicate these findings in dynamic bimanual 1:2 and 2:1 tasks where performers had to move one wrist faster than the other, and to determine the influence of limb dominance. Dominant left-handed (N = 10; LQ = − 89.81) and dominant right-handed (N = 14; LQ = 91.25) participants were required to perform a 2:1 and a 1:2 coordination pattern using Lissajous feedback. The harmonicity value was calculated to quantify the interference in the trial-time series. The analysis demonstrated that regardless of limb dominance, harmonicity was always lower in the slower moving limb than in the faster moving limb. The present results indicated that for dominant left- and dominant right-handers the faster moving limb influenced the slower moving limb. This is in accordance with the assumption that movement frequency has a higher impact on limb control in bimanual 2:1 and 1:2 coordination tasks than handedness

Direct laser-written optomechanical membranes in fiber Fabry-Perot cavities

Integrated micro and nanophotonic optomechanical experiments enable the manipulation of mechanical resonators on the single phonon level. Interfacing these structures requires elaborate techniques limited in tunability, flexibility, and scaling towards multi-mode systems. Here, we demonstrate a cavity optomechanical experiment using 3D-laser-written polymer membranes inside fiber Fabry-Perot cavities. Vacuum coupling strengths of ~ 30 kHz to the fundamental megahertz mechanical mode are reached. We observe optomechanical spring tuning of the mechanical resonator by tens of kHz exceeding its linewidth at cryogenic temperatures. The extreme flexibility of the laser writing process allows for a direct integration of the membrane into the microscopic cavity. The direct fiber coupling, its scaling capabilities to coupled resonator systems, and the potential implementation of dissipation dilution structures and integration of electrodes make it a promising platform for fiber-tip integrated accelerometers, optomechanically tunable multi-mode mechanical systems, or directly fiber-coupled systems for microwave to optics conversion.Comment: 10 pages, 5 figure